Protective means against breaking of tools



Sept. 2,9, 1925.

l. BENK PRoTEc'rIvE:- MEANs AGAINST BREAKING or Toons Filed July 17,1923 2 Sheets-Sheet l IIN- lag. 1

w. :an f

Sept. 29, 192,5, m1,555,098

l. BENK PROTECTIVE MEAN5 AGAINST BREAKING `OF TOOLS FledJuly 17, 192.15`2 Sheets-Sheet 2 2 v g @f Patented Sept. 29, 1'9/25.. y

UNITED STAT-Es 1,555,098 PATENT OFFICE.

A:WAN EENx,v or' VIENNA, AUSTRIA, A SsIGNoa To TEE rml rLExo-INDUsTnIE-GESELLSCHAFT 1u. E. 1I., or VIENNA, AUSTRIA.

PROTECTIVE MEANS AGAINST BREAKING or TooLs Application iled July 17,1923. Serial No. 652,164.

To all whom t may concern.'

Be it known that I, IVAN BENK, a citizen i of the Republic o Austria,residing at Vienna, Austria, have invented certain new and usefulImprovements in Protective Means Against Breaking of Tools, of which thefollowing is a specification.

4 Drilling and screw cutting devices for disconnectingthe drill or toolfrom its 'driv-4 ing member when the stress on itis too excessive or forreleasing an overload clutch and thereby stopping the tool are known.IIitherto such means have been responsive only to torsional stresses onthe tool and have given nok protection against excessive axial pressureso that heretofore only partial protection has been given againstbreaking off the tool whereas the object of the present invention is to'provide for effective protection against breaking -in all .directions.

With the above object in view the present invention may be regarded asconsisting in yproviding a device' which acts protectively againstbreakage of a drill or other tool by reason of either excessive torsionor excessive axial pressure.

More specifically stated theimproved device comprises a yielding clutch`which interrupts the drive of the tool when exces- -sive vstresses 'dueto torsion or axial pressure occur. This clutch conveniently may takethe form of a ball clutch but 'any other clutch may be used havingresilient loading levers adjustable in length or action and may beadjustable in length or faction andl nay be embodied in protectingdevices which come into operation only when torsional or only axialforces come into action. .Clutches hitherto proposedl have afforded aprotection against breakage of the drill if the drill meets with naturalresistances or if the drill is locked by cutting'slduring drilling or bycasting faultsin the' material, but when the drill is exposedtoexces'si'veaxial pressure the drill will be broken particularl in thecase of drills of smaller sizes.v Suc a clutch may be arranged forexample for a drill 4 mm. in diameter and having a feed of 0.1 mm. Inorder to` obtain this feed with a sharp drill, the operator'must exert apressure of about 50'kgs'. on the drill. If the drill still be sharp anda pressure of from 60 to kg.. is exerted thereon instead-lof 50 kg. thena greater feed as for example 0.15 takes ing operation and this' greateraxial pressure occurs, then a greater removal of cuttings cannot takeplace, but although a greater torsion will be avoided nevertheless agreater axial pressure will occur and if the clutch is not releasedthereby the drill may be broken.

In accordance with the present invention in order to bring the drill toa standstill, in spite of the excessive-axial pressure, in good timebefore breakage occurs, even when the cutting edges have become blunt orwhen hard material is being operated upon, a device is provided by whichwhen' excessive axial presslire occurs the clutch is released and thedrill brought to standstill. In this manner the drill is protectedagainst breaking in every Nvay,`irrespective of the material which isbeing operated upon, 'as soon as'the maximum permissible drill,resistances dependent on the resistive capa'eityof the drill have beenreached and not accord- Y show by way of example several structural l*embodiments of the invention:

Figure 1 is a longitudinal section whereinthe various parts of thedevice are visible. Figure 2 illustrates how the necessary axialpressure between the clutch.parts 'can be adjusted byan'ad-'iisting cap,and 4 1jligure 3 shows t"iadjusting `spring in p an. v

Figure v4:.is a longitudinal Section similar to Fig. 1 of theanti-torsion overload clutch"A as a complete unit.

F'gure. 5 is a horizontal section correspending with Fig. 4 below thesprings looking upwards.

Figure 6 shows the lower clutch dise in Fig. 4 seen from above.

Figure 7 shows a second constructional form for adjusting the axialpressure.

Figure 8 shows the corresponding adjustable springs in perspective andseen from underneath, and Y Figure 9 illustrates how an overload clutchaccording to the invention is embodied into a chuck.

Figure 10 shows an embodiment of the invention with a friction discclutch.

In the driving member 1 may be seated a shaft 2 forcentering the drivenmember 3, the members 1 and 3 being coupled together by an overloadclutch 4 (Fig. 4) of which the capacity for power transmission isadjustable by adjustable loading arms or springs. The clutch may beformed by a ball clutch or a ball locking clutch which also has theadvantage that the cle-clutched parts move relatively with rollingfriction. The clutch is provided with two clutch discs 4 and 4b, betweenwhich are arranged the balls 4,.preferably seatedin a ball cage 4 sothat they always remain at the same distance apart, and on the surfacesof the clutch discs 4 and 4", turned towards each other, there areprovided, adjacent the balls, corresponding recesses 4e in which theballs engage when the clutch is engaged and out of which they roll whenthe clutch is disengaged. The clutch disc 4fL is directly engaged by thedriving member and for this purpose engages by means of lugs 41 (Fig. 4and Fig. 6) iii vertical slots 1 (Fig. 2) of the hollow casing -1h ofthe` driving member which is adapted to receive the parts of the clutch.Over this casing 1b may also be placed an enclosing cap 5 which maybetween said part 1" and the upper bearing surface which latter may berigid or yielding and resilientyielding bearing surfaces being providedfor limiting the axial feed pressure.

By adjusting the springs 6 in relation to the pins or projections 4 themagnitude of the releasing resistance of the clutch may be varied andthe clutch is rendered suit-able for the transmission of the' smallesttorsional moment when the free ends of spring arms 6, 6", 6c bearagainst the pins 4f, as in consequence of the longest lever arms thespring action is weakest the spring arms escaping more easily when theallowable torsional stress is exceeded. If the spring arms 6 are rotatedaround the longitudinal avis of the device so that the bearing points ofthe pins 4f move towards the base of the spring arms the leverage of thespring arms becomes gradually shorter the spring action becomes strongerand the clutch is therefore capable of transmitting larger torsionalforces. In the arrangement according to Fig. 1 the movement of theloading springs 4 is effected by the enclosing cap 'the latter beingconnected to the-springs by means of a pin 12. The adjustment may beeffected according to a scale and for this purpose graduations areprovided on the driving part 1 (Fig. 2)I which directly indicate theadjustmentwhicli should be effected for a particular diameter of toolthe mark Z on the enclosing cap being moved so as to coincide with thecorresponding graduation on the part. j

The clutch also serves `to protect the tool against overload by a toohigh axial feed pressure as it also interrupts the drive in this case sothat the tool is not liable to be broken by a too high axial pressure.On the other hand a visual or audible indicatserve as adjusting memberfor the overload )ling device may be provided to indicate when clutch orin the constructioiial form according to Fig. 1 as adjusting member forthe various adjustable parts of protecting device. For adjustingtheclutch resistance of the overload-i clutch against cle-clutching,-disc like loading springs 6 are provided.

. These springs may have curved spring arms,

as shown in Fig. and these spring arms 6, 6, 6 bear against pins orprojections 4f which project from the underside ofthe clutch disc 4 andare pressed against. these projections 4f by a predetermined pressure,by means of the central pressure ring 7, which is pressed against thesprings by a nut 8, the nut being screwed on the internal screw thread 9of the` driven part 3. For reducing the friction between the ring 7 andlthe loading springs 6, aball bearing 10 is interposed between saidsprings and ring. The driven part 4" of the clutch may be formed as anannular flange'on the vdriven part 3, and a ball bearing 11 isinterposed the permissible axial pressure has been clutch 4, preferablythe annular flange 4b thereof is supported against an adjustable bearingsurface which is in the form of an elastic abutment interposed' betweenthe driving part 1 and clutch flange 4b. Thel elastic abutment may becomposed -of springs 13 which may be formed as disc springs or as sringarms with adjustable arm lengths and the etlective length of arm isdetermined by pins 14 which Contact with spring arms the pins orprojections 14 being provided on the driving part 1. Adjustment may beeffected as in the case of the springs 6 by rotating the springs 13around the longitudinal axis ofthe device and for this purpose thespring 13 or one of the spring arms 13, 13", 13 is provided with ahandle 13d, which may be operatedby hand or by the enclosing cap 5, thelatter v 'I form of lconstruction being shown in Figs. ed to the part 1by a wire ring 17 (Fig. 1).

1 and 2, the extension 13d of the springs engaging with a' slot 5a inthe enclosing cap and on turning the cap the springs are moved aroundthe axis of the`device.. Ihe extreme positions of adjustment are limitedby a horizontal slot 1o provided in the .hollow casing 1b, the slot 1dof the casing (Fig. 2) being used solely for the purpose of 1n-'troducing the spring 13with its handle'13d into its operating position.In the case of the springs 13a, 13b, 13, the resiliency of the springincreases with the increaseof the distance ofthe bearing point 14 fromthe base or root of -the spring arm and the spring actionthus becomeweaker as the distance from the base or root of the arm increases whilstwhen the spring arm or loadingarm becomes shorter the spring ac-` tionbecomes stronger. The adjustment of the springs 13 against exceeding theper missible axial pressure is eiected generally by the adjusting cap 5,the springs 6 and 13 being chosen independently of each other and beingof such dimensions that the set position of the overload springs againsttorsion for a given diameter of tool coincides with 'the overloadposition for preventing the axial pressure for the same tool beingexceeded. f

As the lugs 41a, of the `clutch ring 4. are

.directly supported by the uppery wall of the vertical slot 1a of'thevdriven part that means that xpart 1b is sitting upon the lugs 4a,then when exerting the axial feed pressure ,in the direction from top tobottom in Fig. 1 the same counter pressure is transmitted from the toolto the driven part and theball bearing 11 or the abutment 'therefor bythe drill chuck 15 mounted on the driven part 3. This yielding vabutmentis formed by the spring 13 and "when the axial feed pressure andthereforej also the counter pressure exceed the value whichV the springs13 canl absorb according to their position, these springs or the springarms will-yield andthe abutment 11 for the ball ,bearing will recede sothat the'driven part moves upwards whilst the position of the clutchdisc 4a remains unchanged or can only take partin a portion of the axialmovement of the locking ring, after the lugs 4&1 engage with the end ofthe slot 1EL so that the balls 4 of the clutch pass out of. the

y recesses and the clutch or drivev is disengage The driven part mayalso be connected directly with the indicating device, which for examplemay consist of a disc 16 which is screwed on the threaded portion 9ofthe driven part and which is disposed at a determined distance fromthe bottom of., the

A enclosing cap 5, the reduction,.of 'this distance indicatingtheincrease' of the axial feed pressure. The cap 5 is rigidly connect- Thedistance betweenparts 16 and 5 should not be allowed to become equal tozero.

to. such an extent ythat the lugs 4?, of the clutchf ring disc 4 aredisposed at a dis- The supporting spring 13 may be tensionedy tance fromthe upper wall ofthe vertical slot 1a during normal operation so that`as the distance of the indicating disc 16 from from each other andproduce the disengage.- y Y ment of the clutch, but this only occursafter the lugs 4a, reach the wall of the slot and after furthersubsequent -movement of the indicating disc 16 or the drivenpart hastaken place.

If on the other hand the axial feed pres-` sure is reduced thesprings 13return to their normal supporting position, the clutch balls '4c rollinto the recesses, 'the clutch being -thus automatically re-engaged sothat the` tool can take part in an operative movement.

The springs 6 and-13 may be disposed singly or in any desired onumberabove one another. Inmthe form of construction illus- 4trated in Figs.1-6 the springs are arranged.

in pairsand the lever arms thereof can be formed of increased sizetowards the base or root the cross section breadth, and thickH ness ofthe arms increasing towards the base. W'hilst the double springsaccording to Figs. 1-6. can be moved simultaneously, the arrangementaccording to Figs.f7 and 8 may also be such that one spring 18 remainsstationary whilst the other spring 19 is movable relatively thereto.-Both springs can also be formed as disc springs having spring varmsarrangedin a circle and can be pro- 'vided with supportingrpins 20,which are secured to the arms of one spring. for example 19, and slideon the. arms .of thel other springs. If then the pins 20' engage withthe longest lever arm of the arms 18 the spring actionis weakest and thesprings are in a position to transmit only the smallest axial'.pressure, whilst when the4 lever arm `ing the permissible axial feedpressure in."

hand tools for example` stocks andthe like also as a tool holder or indrill cliucks 130.`

The springs 18 are prevented .Y

vasalso in iiiachine tools when it is arranged in any suitable positionsin` the drilling spindle or'in the feed spindle where it may be used inconjunction with the controlling device of the machine driving mechanismand as a releasing means for the control device. For instance it is alsopossible to arrange 'the overload clutch against ,tor-

sional overstrai'n or against axial oversti'ain or against overstrainsin both directions n into thesupport of a lathe or of any other toolmachinery. l

Figure 9 shows avertical cross section through a chuck in the interiorMof which the clutch is securely arranged. The parts 'eorersponding intheir function to those of Fig. lV respectively of Fig/4 have the samereference numbers although their positionand shape is partly differingthereof. *igure 10 shows a broken off section .through an embodiment ofthe overload clutch device provided with friction discs l? in place ofthe ball clutch. Here also the parts with the'samefunction as those inFig. 4 bear the same reference numbers.-

H yeach other, the `adjacentfaces of the said discs being provided withrecesses having inclined side walls, balls located `between such disesand adapted to engage into the said recesses, a resilient bodyinterposed between the clutch member positively revolving with thedriving element and a stop g member supported by the driven element, a

second resilient body interposedbetween the driving element andtheclutch member positively revolving with the driven element, the-latterresilient' body being elastically deformed whenever the axial pressureonthe tool exceeds a predetermined vlimit the clutch `member associatedtherewith receding from the other lclutch member.

2. A slip drive for drill chucks, compris- I ing, a driving element, adriven element and an overload clutch interposed between the saidelements, such clutch comprising two discs atlright angles to the axisof the tool, and ladapted to move axially relatively vto eachother, the(adjacent faces of thesaid discs :being provided' with' recesses havinginclined* s1de walls,'balls locatedbetween Y,

such discs` and adapted to engage into the said recesses, aresilientbody interposed between the clutch -member positively revolving with thedriving element' and a stop member supportedby the driven element, suchclutch'member being adapted` to move axially relatively to the saiddriving inember, a stop provided on the latter for limiting the axialmovement of this clutch meniber, a-second resilient body interposedbctween the driving element and the clutch member'positively revolvingwith and fast on. the driven element,- tlie latter resilient body beingelastically deformed whenever the'axial pressure on the tool exceedsl apredetermined limit, the clutch member associated therewith recedingfroml the other clutch member.

3. A slip drive for drill chucks, comprising, a driving element, adriven element and an overload clutchinterposed .between the saidelements such clutch comprising two discs at right angles to the axis ofthe tool, and ,adapted tofmove axially relatively to veach other, theadjacent faces of the said "discs being provided with recesses havinginclined side walls, balls located between such vdiscs and adapted toengage into the said recesses, a resilient body interposed between theclutch member positively revolving -with the driving element and a stopmember supported by the driven element, such clutch memberbeing adaptedto move.

- axially relatively to the said driving membei', a stop provided on thelatter for lim-'- iting the axial movement of this clutch member, asecond resilient body interposed between the driving element and theclutch member positively revolving with and fast on the driven element,the latter resilient body being elastically deforined whenever the axialpressure ,on the'tool cxcedesa predetermined limit, the clutch member.:issociated thereto receding from the other clutch member, indicatingmeans fast on the driven element, and means for ascertaining the'positioni` of the indicating `means relatively tothe above said stopcorresponding to\the permissible maximum axial strain on the tool.

, 4. A slip drive for drill chucks, comprising, a driving element, adriven element and an'overload clutch interposed between the saidelements, a resilientbody acting on one of the said clutch members, suchresilient body comprising a central portion, substantially radialequidistant arms projecting therefrom, segments extending from the freeends of such radial arms such resilient body being interposed betweenone of said elements and one of the clutch members, the centralportionbeing supported on one of the last named parts and the segments restingen pins projecting from the other of the last named parts' and means forturning the said resilient body round the axis of the said other of thelast named parts. i

5. A slip drive for drill chucks, ycomprising a drivingelement, a drivenelement andan overload clutch interposed 'between the said elements, aresilient body acting on one of the saidclutch members, such res il.vlent body comprising a central portion, substantially radial equidistantarms projecting therefrpm, segments extending from the?v free ends ofsuch radial arms,- the fiexibilit,I oisuch segments decreasing fromtheir ends towards the said radial'arms, such resilient 'body beinginterposed betweenone of said elementsandone of the clutch'members, theVcentral portionbeing supported on one otl the last`named parts andthesegments rest-4 ing on pins projecting from the other of the last namedparts and means for turning the said resilient body-round the axis ofthe said other of the last namedparts.

6. A slip drive Vfor drill chucks, comprising a driving element, a'driven element and an overload clutch interposed between the saidelements, a resilient body acting oncone oi the said clutch members,such'r'esilient body comprising a plurality of superposed springs eachconsisting of va central por' tion, equidistantradial arms projectingfrom' such central portions, segments extending from the' free ends ofsuchradial arms, such resilient body being interposed between one ofsaid elements and one of they clutch members, vthe central portion beingsaid-other of the last'named parts, one of 'supported on one of the lastnamed parts and the segments resting on pins vprojecting from the otherof the last named parts and means for turning the said resilient bodyround the axis of the said other of the last named parts.

7; Avslip drive -for drill chucks, comprisf ing a drivingelement, adriven element and an overload. clutch lnterposed between the saidelements, such clutch comprising two members ladapted to move axially.relatively t'oeach other and clutching elements located between suchmembers, resilient bodies, one forl each of the clutch members actingaxially upon its associated clutch member, each of such resilient bodiescomprising a central portion, substantially', radial equivdistant armsprojecting therefrom and seg' ments'extending Jfrom the free ends ofsuch 'radial arms, each of such `resilient bodies being interposedbetween one of said' elements and 'one of the clutch members,`thecentral portion being supported on one .of the last lnamed partsand these Ientsrest-v ing on pins projecting from t e other of the last namedparts and means for turning the said resilient body round the'.` axis-ofthe thesefresilient bodies being elastically deformed whenever the axialpressure on the tool exceeds a predetermined limit, the 'clutch memberassociated therewith receding Jfrom `the other clutch member.

8. A slip drive'fffor'drill chucks, comprising, a driving element, adriven element and an overload clutch interposed between Vthe saidelements, Such clutch, Comprising two .terposed between one of saidelements and :members adapted to move axially relatively to each otherand clutching elements located p between lsuch members, resilientbodies,- one j for each of the clutch members acting axiallyupon itsassociated clutch member, each `of .such resilient bodies comprising aplurality ofsuperpo'sed springs each consisting of aeetral portion,equidistant-radial arms projecting from such central portionsandSegments 'extending from 'the .free ends ot'- such radial arms,A 'eachof suph resilient bodies being interposed between one ofsaid "elements,and one of the clutch members, the 'central portion being supported onone-of vthe last vnamed parts and the segments rest-- ing' on pins'projecting fromthe other of the last named parts andmeans for turningthe said resilient body round the axis of the said other of the lastnamed parts, one of lthese resilient bodies being elastically de-vformed whenever the axial pressure onthe` tool 'exceedsa predeterminedlimit, the clutch member'associated therewith receding 'from'the otherclutch member. l

9. A slip drive for drill chucks, compris' ing, a driving element,- adriven element and an'overload clutch interposed between the ysaidelements, such clutch comprising two l inembers adapted tol move axiallyrelatively to each other and` clutching'elements' located. between suchmembers, resilient bodies, one' for each of the clutch members actingaxial-5 ly upon its associated clutch member,l eacb. of such resilientbodies comprisinga central portion, substantially radial equidistantarms projecting therefrom'and segments extending from the free ends ofsuch radial arms each of such resilient bodies being inone of theclutchmembers, the central portion being supported lon one of the last namedparts and the segments resting on pins projecting from the other of thelast named parts and means for turning the said resilient body round theaxis of the said resilient bodies being elastically deformed Wheneverthe axial pressure onthe tool ex- .other of the `last named parts, oneof these ceeds a predetermined limit, the clutch mem two members adaptedto move axially relatively 'to each other and clutching elements locatedbetween such members, resilient bodies, one for each of the clutchmembers acting axially .upon 'its associated clutch` member, each ofsuch .resilient bodies comprising a, central'portion, substantiallyradial equidistant arms projecting therefrom and segments extending fromthefree ends of such radial arms, each of such resilient bodies beinginterposedbetmveen one of said elements and one of the clutqh members,the central portion being supported on one of the last named parts andthe segments rest-- ing on pins projecting from the-other of thel lastnamed parts and means for turning 'the lsaid resilient body round theaxis of the said Y other of the last named parts, one of these resilientbodies being elast-ically deformed ture.

Whenever the axial'pressure on the tool eX ceedsa predetermined limit,the clutch member associated therewith receding from the other clutchmember and a casing adapted to be rotated and" locked in position on thedriving element and enclosingthe clutch members and theresilient bodies,the latter being provided' with projections engaging the said easing,andP means form indicating the position of the easing relatively to thedriving element. f

In testimony whereof I aiix my signarIVAN BENK.

